The present invention relates to an ink jet printing apparatus which forms letters and pictures by means of ejecting ink droplets onto a print medium.
The present invention also relates to an ink jet printing method. According to this method, dye containing color ink is ejected on the print medium so as to mix or react with colorless or light colored liquid (print quality improver liquid) which contains various compounds capable of rendering the dye in the ink insoluble, thereby producing a highly reliable print with improved water resistance, light resistance, or the like properties, or a high density image of high quality, which suffers little from feathering or color bleeding.
Further, the present invention relates to a color ink jet printing method for printing color images clearly and with high density. More specifically, it relates to a printing method in which a set of color inks, such as yellow (Y), magenta (M) and cyan (C), or green (G), red (R) and blue (B), is used in combination with black (Bk) ink.
The present invention is applicable to all of the apparatuses which use a print medium such as paper, fabric, leather, unwoven fabric, or the like, as well as metals. As for specific examples of such apparatuses, it is possible to list office equipment or industrial production equipment, such as printers, copying machines, or facsimiles.
The printing method based on the ink jet system is widely used in printers, copying machines, facsimiles, and the like since it is advantageous in that the operating noise is low, the running cost is low, its size can be easily reduced, or it can be easily converted to print color images.
However, in order to produce xe2x80x9chighly reliable printed productsxe2x80x9d or xe2x80x9cprinted images of high qualityxe2x80x9d using the conventional ink jet printing method, it was necessary to use specific paper suitable for the purpose; in other words, it was necessary to use dedicated paper with an ink absorbing layer. In recent years, a method has been put to practical use, which accomplishes these objectives by means of improving the ink so that the desirable results can be obtained using xe2x80x9cplainxe2x80x9d paper used in large quantity in the printer or copying machines. However, the level of quality reachable using this method has been unsatisfactory.
As for the method in which the ink is modified to improve the water resistance of the image, a method has been known, in which the water resistance is given to the coloring material contained in the ink. The problem is that the ink used in this method is rendered difficult to re-dissolve in the water once the ink dries; therefore, it is liable to plug the nozzles of the printing head and also makes the performances of the plugged nozzles difficult to restore. Of course, these problems can be prevented, but the prevention requires a complicated structure.
Japanese Laid-Open Patent Application No. 84,992/1981 discloses a method, in which the print medium is coated in advance with a material capable of fixing the dye to the print medium. This method, however, requires the use of a specific print medium, and also, cannot prevent increases in the size and cost of the apparatus, since the material for fixing the dye has to be coated. Further, it is rather difficult to reliably coat the dye fixing material to a predetermined thickness.
Also, Japanese Laid-Open Patent Application No. 63,185/1989 discloses a technology for adhering to the print medium a type of colorless ink capable of rendering the dye insoluble, using an ink jet printing head. In this method, the dot diameter of the colorless ink is rendered larger than that of the dot diameter of the printing ink; therefore, even when the landing points of the printing inks and colorless ink are displaced from each other, a satisfactory print or image quality can be obtained.
However, this method also suffers from several shortcomings. This method ejects the colorless ink across the entire surface where the images are to be formed; therefore, a large amount of the colorless ink is consumed, and as a result, the running cost increases. Also, since more than the usual amount of ink is ejected onto the print medium, it takes a longer time to dry the ink, and also, the landing points of the inks are displaced from each other because of the cockling of the print medium, which occurs as the ink adhered to the print medium dries. In particular, when a color image is formed, the cockling, which leads to the misalignment of the landing points, greatly deteriorates the image quality. The patent application being discussed here does not disclose any method for optimizing the amount of the colorless ink to be adhered to the print medium, according to the type of the print medium. Further, the colorless ink is ejected even when the high quality is not required, for example, even when the recording is made in a draft mode; therefore, the colorless ink is wastefully consumed. Further, the liquid permeation into the print medium varies depending on environmental factors such as the ambient temperature or humidity; therefore, there are times when the dye insolubilizing colorless ink fails to mix or react ideally with the image producing ink, and as a result, the dye is not made insoluble.
Also, the liquid differently permeates the print medium, depending on the type of the print medium; therefore, there are times when the dye insolubilizing colorless ink fails to mix or react ideally with the image producing ink, and as a result, the dye is not made insoluble.
Therefore, this method suffers from another shortcoming. Namely, when the dye is not made insoluble, the feathering or bleeding occurs and degrades the print image. Here, xe2x80x9cfeatheringxe2x80x9d represents a phenomenon where the bleeding ink leaves on the print medium, a pattern of trails that looks like a feather, and xe2x80x9cbleedingxe2x80x9d is a phenomenon where the color inks mix with each other on the print medium after they are deposited thereon.
There have been disclosed a large number of conventional technologies which are intended to improve the fastness of the print. Japanese Laid Open Patent Application No. 24,486/1978 discloses a technology which improves the resistance of the dyed product against humidity. According to this technology, the dyed product is put through a process in which the dye in the dyed product is turned into lake so that it is firmly fixed.
Japanese Laid-Open Patent Application No. 43,733/1979 discloses a printing method, in which an ink jet printing system is used in conjunction with two or more ink components, which increase their film forming capacities as they make contact with each other under normal or heated condition; wherein those components are allowed to make contact with each other on the print medium so that a film capable of adhering firmly to the print medium is formed.
Japanese Laid-Open Patent Application No. 150,396/1980 also discloses a method in which an agent capable of forming the lake with the water soluble dye in a water based ink is applied after the ink jet printing.
In Japanese Laid-Open Patent Application No. 128,862/1983, an ink jet printing method is disclosed, in which it is anticipated where the image producing ink is deposited, and the image producing ink and the processing ink are deposited thereon in an overlapping manner. According to this method, the processing ink may be deposited before the image producing ink, or may be overlaid on the image producing ink deposited before the processing ink; or the image producing ink may be overlaid on the processing ink deposited before the image producing ink, and thus deposited image producing ink may be covered with the processing ink.
However, the problems that might have occurred through practical applications of these printing methods have not been disclosed in these journals which present these prior technologies.
Further, no method has been disclosed in these patent applications, in which when two or more inks of different color are used, the processing liquid (print quality improver liquid) is made to react with only the ink of a specific color, nor has there been disclosed a method in which a recording mode suitable for a specific purpose can be selected from among a number of available recording modes.
Also, no method has been disclosed, which can minimize the amount of the processing liquid to be applied to the area which basically has no bearing on the printing results.
The present invention was made in consideration of the aforementioned problems, and its object is to obtain a xe2x80x9creliable print,xe2x80x9d which displays better water resistance and light resistance, and faster fixation than those of the conventional print, even when plain paper is used as the print medium.
Another object of the present invention is to provide an ink jet printing method and a printing apparatus, which are capable of producing a xe2x80x9chigh quality printed imagexe2x80x9d which has high density and highly developed colors, and does not suffer from feathering or color bleeding.
Another object of the present invention is to provide an ink jet printing method and a printing method, which are capable of depositing efficiently the print quality improver liquid on the print medium, without wastefully consuming the print quality improver liquid.
Another object of the present invention is to provide a printing method in which an optimal process is carried out depending on the print medium type, for example, whether the print medium is the OHP transparency or something else, so that a high quality image with the highest water resistance can be obtained.
A further object of the present invention is to provide a printing method in which the amount of the processing liquid to be ejected is minimized to reduce the running cost X, while producing a high quality image having a minimum amount of cockling.
Another object of the present invention is to improve the fastness of the ink fixation to the print medium, the water resistance of the produced image, and the color development of the produced image, and to minimize the color bleeding among two or more color inks, by means of causing the print quality improver liquid to mix or react with the ink, on the print medium.
In other words, the ink jet printing method in accordance with the present invention is such an ink printing method that coloring material containing color ink and colorless or lightly colored liquid (hereinafter, print quality improver liquid, or P liquid) containing components capable of rendering the ink components insoluble or aggregating them are ejected onto the print medium, where the ink mixes and/or reacts with the P liquid to produce a highly reliable image of high quality.
The data to be used for ejecting the P liquid are derived from the data to be used for ejecting the color inks: yellow (Y), magenta (M), cyan (C) and black (Bk) inks.
Further, this printing method provides two or more printing modes, and the amount, type, or the like of the P liquid to be ejected is determined according to the selected mode. In this case, the data for ejecting the P liquid may be differently composed depending on whether the Bk ink or the Y, M and C inks are ejected, and also, the printing timing may set up so as to provide a lag between the P liquid and the Bk, Y, M and C inks.
In the present invention, the terminology, xe2x80x9cprint quality improvement,xe2x80x9d includes: the improvement in image properties such as the density, saturation, sharpness of edge, dot diameter, or the like; the improvement in the fixability of the ink; the improvement in the durability related properties of the image, such as the weather resistance, water resistance, light resistance, or the like; and the suppression of bleeding, feathering, and the like. The print quality improver liquid is liquid contributing to the improvement of the print properties, and includes liquid capable of insolubilizing the dye contained in the ink, liquid capable of disturbing the state of pigment dispersion in ink, as well as the like liquids. Here, the terminology, xe2x80x9cinsolubilizexe2x80x9d refers to a phenomenon that anionic radicals in the ink dye and cationic radicals in the cationic substance contained in the print quality improver liquid ionically react with each other, being thereby ionically bonded, and as a result, the dye in the state of being uniformly dissolved in the ink separates from the ink solution. It should be noted here that even when the dye in the ink is not entirely rendered insoluble, the present invention can effectively suppress the bleeding and can improve the color development, the letter quality, the fixability of the ink, and the like. Further, when the coloring material used in the ink is the water soluble dye containing anionic radicals, the terminology, xe2x80x9caggregate,xe2x80x9d has the same meaning as xe2x80x9cinsolubilize,xe2x80x9d but when the coloring material in the ink is pigment, it also means that the pigment dispersant or the pigment surface tonically interacts with the cationic radicals of the cationic substance contained in the print quality improver liquid, and as a result, the state of the pigment dispersion is disturbed, which results in the increase in the pigment diameter. Normally, as the aggregation progresses, ink viscosity increases. It should also be noted that even when the pigment or pigment dispersant in the ink is not entirely aggregated, the present invention can effectively suppress bleeding and improve the color development, the letter quality, the fixability of the ink, and the like.
In the present invention, the P liquid can be optimally used according to the selected printing mode; therefore, the power source capacity of the printing apparatus can be reduced, which makes it possible to reduce the apparatus size as well as its cost.
The present invention relates to an ink jet printing method, which, in order to accomplish the aforementioned objectives, uses the print quality improver liquid, which is mixed or caused to react with the colored inks (Y, M, C and Bk inks) on the print medium, in response to the imaging data. The type and amount of the print quality improver liquid are optimally selected depending on environmental factors such as the ambient temperature and humidity, and/or the type of the print medium; therefore, it is possible to always obtain a xe2x80x9chighly reliablexe2x80x9d image with xe2x80x9chigh qualityxe2x80x9d regardless of the environment and/or the type of the print medium.
In the present invention, the xe2x80x9cadjustmentxe2x80x9d of the amount of the print quality improver liquid includes selecting xe2x80x9cnon-ejectionxe2x80x9d of the print quality improver liquid, as well as determining the amount of the P liquid to be ejected Per unit area of the print medium.
According to the present invention, when the print quality improver liquid and the inks are mixed on the print medium, the higher the ambient temperature is, and the lower the humidity is, the less the print quality improver liquid is used.
The reasons why such a control that uses a smaller amount of the print quality improver liquid as the ambient temperature becomes higher, and the humidity becomes lower is effective are as follows:
(1) The higher the temperature, the shorter the time it takes for the print quality improver liquid and the color inks to mix or react with each other, and the more efficiently they do so, while they permeate from the surface of the print medium thereinto; therefore, the necessary amount of the print quality improver liquid to be mixed or caused to react with the inks may be less. (2) The lower the humidity, the more difficult it is for the ink to permeate into the print medium. Therefore, the time necessary for these liquids to permeate into the print medium from the surface thereof becomes longer, affording thereby enough time for the print quality improver liquid to mix or react satisfactorily with the colored inks.
An excessive amount of the print quality improver liquid produces contrary results; it induces feathering of the colored inks. Further, the print quality improver liquid is replenished from the container as it is consumed. Therefore, minimizing the print quality improver liquid usage can also reduce the running cost.
The temperature based control of the Tw of the print quality improver liquid and the humidity based control of the Tw of the print quality improver liquid may be independently executed. Though detection of the humidity alone may be effective in some degree, the best results can be obtained when the control is executed on the basis of both the temperature and humidity.
In the following embodiments of the present invention, a case in which the Tw is controlled in order to control the amount of the print quality improver liquid to be ejected is described, but the present invention is not limited by this case. For example, when the amount of the print quality improver liquid is increased by means of controlling the temperature of the print quality improver liquid head unit, the temperature may be increased in order to increase the amount of the print quality improver liquid. Other means may be employed.
Further, when the print quality improver liquid is selectively used on the basis of the user""s objective, and/or the characteristic of the printing ink to be used, it is possible to produce a xe2x80x9chighly reliablexe2x80x9d printed product with improved water resistance and light resistance, and the like, and a printed image of xe2x80x9chigh qualityxe2x80x9d which displays preferable color development and high density while suffering little from feathering and color bleeding.
According to an aspect of the present invention, the print quality improver liquid and inks are caused to mix or react with each other on the print medium, so that the water resistance and color development of the printed image are improved; color bleeding among two or more color inks is minimized; and the fixability of the ink to the print medium is improved.
According to another aspect of the present invention, three modes are available, which are manually or automatically switchable, page-by-page, and/or in the middle of each page. In other words, the printing mode is discriminated with reference to the printing area so that the print quality improver liquid can be properly applied. Therefore, it is possible to minimize the amount of the print quality improver liquid consumed during the printing, without losing the effectiveness of the liquid.
According to another aspect of the present invention, the liquids (including the inks) are ejected in the following order: non-black ink, print quality improver liquid, black ink. Using this order can assure the effects of the print quality improver liquid. This is because of the following reason: when the liquids are ejected in a different order, for example, non-black ink, black ink, print quality improver liquid, the print quality improver liquid is going to be ejected after bleeding occurs between the non-black ink and black ink.
According to another aspect of the present invention, the amount of the image producing ink to be ejected onto the area where it is overlaid on the print quality improver liquid is increased relative to where it is not overlaid. This is because the reaction between the print quality improver liquid and ink stops the permeation of the ink at the location of the reaction, resulting thereby in a smaller dot diameter.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings.